Joseph “Joey” Meek Jr., 21, a friend of Dylann Roof, the man charged in the killing of nine people at a Charleston, South Carolina, church, was arrested by the FBI Thursday afternoon. He was taken into custody while at work, his girlfriend Lindsey Fry told the State newspaper.

Meek received a letter Aug. 6 from the U.S. Attorney’s Office in Columbia, South Carolina, informing him he was a “potential target” in the investigation of the Charleston shootings in June, in which Roof gunned down nine African-Americans at a historically black church. The letter stated Meek was under investigation for lying to law enforcement and for failing to report a crime. It also informed Meek of his constitutional right to an attorney and advised him of his right to remain silent. The letter gave him until Aug. 21 to a respond to the U.S. Attorney’s Office.

In this photo provided by the Charleston County Sheriff's Office Detention Center, Dylann Storm Roof is seen in his booking photo after he was apprehended as the main suspect in the mass shooting at the Emanuel African Methodist Episcopal Church that killed nine people on June 18, 2015, in Charleston, South Carolina. Photo: Getty Images

Roof stayed with Meek and his family in their mobile home in Red Bank, South Carolina, before the shootings. In an interview in June, Meek said Roof had complained about blacks when he was drunk and had said "blacks were taking over the world" and that "someone needed to do something about it for the white race." Meek also knew Roof had bought a gun and said that he had hidden the gun from Roof during his drunken rant until he had sobered up, the Associated Press reported.

Meek reportedly told the state Tuesday that he did not believe he committed any crimes and said he called authorities after seeing Roof’s picture on TV in connection with the shootings.

No one else in the mobile home that Roof stayed at before the shootings has received a "target" letter. Roof, 21, is facing federal hate crime charges and nine counts of murder in state court. The state has said it will seek the death penalty, but Roof's attorneys have said he is willing to plead guilty in exchange for a life sentence.